C-peptide and HOMA-IR variants accurately identify insulin resistance in diabetic dogs

In canine diabetes mellitus, insulin resistance (IR) is a frequent and challenging complication, significantly hindering effective glycemic control and contributing to broader metabolic dysfunction. Current diagnostic methods for IR in dogs can be invasive or lack precision, creating a critical need for reliable, non-invasive biomarkers. Understanding the utility of markers like C-peptide, a byproduct of insulin synthesis, and its derived indices such as HOMA-IR, could provide veterinarians with crucial tools for early detection and improved management of diabetic dogs.

A cross-sectional prospective study enrolled 76 dogs from a referral center, categorizing them into four groups: Healthy (n = 17), Pre-diabetes mellitus (PreDM) (n = 11), Insulin-dependent diabetes mellitus (IDDM) (n = 20), and Insulin-resistant diabetes mellitus (DMIR) (n = 28). Fasting blood samples were collected from all dogs and analyzed for glucose, C-peptide, and other metabolic indicators. Researchers then determined and compared HOMA-IR by C-peptide, HOMA-IRCP2, and HOMA2-IR values across these groups to assess their diagnostic utility for IR.

The DMIR group consistently exhibited the highest levels of C-peptide and all three calculated HOMA-IR variants (HOMA-IR by C-peptide, HOMA-IRCP2, and HOMA2-IR), indicating a strong correlation with insulin resistance. Receiver Operating Characteristic (ROC) curve analysis confirmed the diagnostic capability of these markers for identifying IR, with statistically significant area under the curve (AUC) values. C-peptide showed an AUC of 0.843 (95% CI, 0.756-0.930), HOMA-IR by C-peptide achieved 0.897 (95% CI, 0.819-0.975), HOMA-IRCP2 reached 0.893 (95% CI, 0.812-0.973), and HOMA2-IR was 0.789 (95% CI, 0.686-0.893), all demonstrating high accuracy (P < 0.001).